Reload a project changed on disk, fingerprinted by its manifest and image sizes (12.13a)

src/IO/ProjectDigest.cpp

@@ -0,0 +1,37 @@
+#include "IO/ProjectDigest.h"
+#include <QCryptographicHash>
+#include <QDir>
+#include <QFile>
+#include <QFileInfo>
+#include <QtEndian>
+#include <algorithm>
+#include <stdexcept>
+
+QByteArray ProjectDigest::compute(const QString &path)
+{
+    QCryptographicHash hasher(QCryptographicHash::Sha256);
+    QFile manifest(path + QStringLiteral("/manifest.json"));
+    if (!manifest.open(QIODevice::ReadOnly))
+        throw std::runtime_error(manifest.errorString().toStdString());
+    // A failed read comes up short; Swift's Data(contentsOf:) throws.
+    const QByteArray bytes = manifest.readAll();
+    if (bytes.size() != manifest.size())
+        throw std::runtime_error("the manifest could not be read whole");
+    hasher.addData(bytes);
+    // Assets are not read: a save would wait on each.
+    const QDir images(path + QStringLiteral("/images"));
+    QStringList names = images.entryList(QDir::AllEntries | QDir::Hidden | QDir::System | QDir::NoDotAndDotDot, QDir::Unsorted);
+    std::sort(names.begin(), names.end());
+    for (const QString &name : names) {
+        const QFileInfo info(images.filePath(name));
+        // Gone mid-listing: half written, as Swift's resourceValues throws.
+        if (!info.exists() && !info.isSymLink())
+            throw std::runtime_error("an image went while the package was read");
+        if (info.isSymLink() || !info.isFile())
+            continue;
+        hasher.addData(name.toUtf8());
+        const quint64 size = qToLittleEndian(quint64(info.size()));
+        hasher.addData(QByteArrayView(reinterpret_cast<const char *>(&size), sizeof size));
+    }
+    return hasher.result();
+}